At the request of a reader, I've done some research on Elvis and the time he spent filming on Florida's Nature Coast. Of course, it wasn't called "Nature Coast" back then. Elvis filmed primarily in Yankeetown, which sits on the Withlacoochee River a few miles inland from the Gulf. This is what I learned after a bit of digging on www.inglisyankeetown.org:
Sources: Citrus County Historical Society and.Visiting Small Town Florida by Bruce Hunt, published in 2003.